Cyanine dyes

ABSTRACT

Disclosed are novel trimethine cyanine dyes, light absorbents, light-resistant improvers, and optical recording media which comprise the trimethine cyanine dyes. The cyanine dyes exert satisfactory solubility and heat resistance when used in high-density optical recording media.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to novel organic dye compounds, andmore particularly, to trimethine cyanine dyes which are useful inhigh-density optical recording media.

[0003] 2. Description of the Prior Art

[0004] As coming into this multi-media age, the following opticalrecording media have been greatly focused:

[0005] (i) compact disc recordable or CD-R, a write-once memory usingcompact disc, and

[0006] (ii) digital versatile disc recordable or DVD-R, a write-oncememory using digital video disc.

[0007] Optical recording media can be roughly classified into inorganicoptical recording media which have recording layers composed ofinorganic substances such as tellurium, selenium, rhodium, carbon, orcarbon sulfide; and organic optical recording media which have recordinglayers mainly composed of light absorbents containing organic dyecompounds.

[0008] Among such optical recording media, organic optical recordingmedia can be usually prepared by dissolving a cyanine dye in an organicsolvent such as 2,2,3,3-tetrafluoro-1-propanol (abbreviated as “TFP”hereinafter), coating the solution on the surface of a polycarbonatesubstrate, drying the coated solution to form a recording layer, andsequentially forming and attaching on the surface of the recording layer(i) a reflection layer made of a metal such as gold, silver or copper,and (ii) a protection layer made of an ultraviolet ray hardening resin.When compared with inorganic optical recording media, organic ones mayhave the drawback that their recording layers may be easily changed byenvironmental lights such as reading- and natural-lights. Opticalrecording media, however, have the merit that they can be made intooptical recording media at a lesser cost because their recording layerscan be directly formed by coating light absorbents in a solution form onthe surface of substrates. Further, organic optical recording media,which are composed of organic materials, are now mainly used as low-costoptical recording media because they are substantially free of corrosioneven when contacted with moisture or sea water and because information,stored in optical recording media by a fixed format, can be read out byusing commercialized readers by the establishment ofthermal-deformation-type optical recording media as organic opticalrecording media.

[0009] What is urgently required in organic optical recording media isto increase their storage capacity to suit for this multi-media age. Theresearch for such an increment, which is now being eagerly continued inthis field, is to shorten the wavelength of a laser beam for writinginformation from 775-795 nm, that is irradiated by conventional GaAlAssemiconductor lasers, to a wavelength of 700 nm or shorter. However,since most of conventional cyanine dyes explored for CD-Rs could notappropriately write and read information by using a laser beam with awavelength shorter than 700 nm when used in high-density opticalrecording media such as DVD-Rs, the cyanine dyes now used could notfulfil the need for high-storage density required in many fields.

[0010] As another causative for spoiling the high-storage density oforganic optical recording media, there may exist problems of the thermaldecomposition and the heat resistance of dyes. In organic opticalrecording media, pits are formed by using heat generated when dyesabsorb a laser beam and then melt and decompose. However, most ofconventional cyanine dyes have a rather lower decomposition point, andthis results in the problem that the part around the pits and otherpit-less part on the recording surface may be easily deformed by theaccumulated heat which is generated when the dyes are exposed to areading laser-beam for a relatively-long period of time because thecyanine dyes have a relatively-low heat resistance.

[0011] High quality products must be provided in large quantity and lowprice to make high density optical recording media such as a DVD-R fix,as an information recording means for multi-media age, in place ofpapers. For the purpose, it is necessary to efficiently coat lightabsorbents on a substrate and make optical recording media with a goodrecording characteristic and higher stability. Light absorbents whicheasily dissolve in organic solvents are essential, and moreparticularly, the development of light absorbents, which less polluteenvironment and easily dissolve in non-halogen solvents, has beendesired. Although various light absorbents were provided and some ofthem have been actually used, no light absorbent, which can satisfy boththe desired light characteristic and solubility, has been realized.

SUMMARY OF THE INVENTION

[0012] In view of the foregoing, the object of the present invention isto provide organic dye compounds which exert satisfactory solubility andheat resistance when used in high-density optical recording media.

[0013] To attain the above object, the present inventors eagerly studiedand screened compounds. As a result, they found that specific trimethinecyanine dyes (may be called “cyanine dyes” hereinafter) whichsubstantially absorb a visible light with a wavelength of shorter than700 nm, are obtainable through a step of reacting benzoindoleniumcompounds bearing a reactive methyl group with benzoindolenium compoundsbearing a suitable leaving group. They also found that, when comparedwith conventional related compounds, most of the cyanine dyes of thepresent invention have the following characteristics: They havesignificantly-high solubility in organic solvents which are frequentlyused in preparing optical recording media, and more particularly,non-halogenated solvents, have decomposition points over 272° C., andhave relatively-high heat resistances. The present inventors confirmedthat the trimethine cyanine dyes form minute pits stably on therecording surfaces and at a relatively-high density when irradiated witha laser beam at a wavelength of shorter than 700 nm in optical recordingmedia. The present invention was made based on the creation of novelorganic dye compounds and the discovery of their industrially usefulcharacteristics.

BRIEF EXPLANATION OF THE ACCOMPANYING DRAWINGS

[0014]FIG. 1 is a visible absorption spectrum of one of the cyanine dyesof the present invention.

[0015]FIG. 2 is a visible absorption spectrum of a conventional relatedcompound.

[0016]FIG. 3 shows the result on DTA and TGA for one of the cyanine dyesof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention solves the above object by providing thetrimethine cyanine dyes represented by Formula 1, which have thesolubility of at least 50 mg/ml in diacetone alcohol (abbreviated as“DAA” hereinafter) at 20° C., and have decomposition points of over 272′(the trimethine cyanine dyes may be called “cyanine dyes” hereinafter).

[0018] In Formula 1, R₁ and R₂ independently represent an aliphatichydrocarbon group which is usually selected from those having up to 8carbon atoms, such as methyl, ethyl, ethynyl, propyl, isopropyl,1-propenyl, 2-propenyl, 2-propynyl, isopropenyl, butyl, isobutyl,sec-butyl, tert-butyl, 2-butenyl, 1,3-butadienyl, pentyl, isopentyl,neopentyl, tert-pentyl, 1-methylpentyl, 2-methylpentyl, 2-pentenyl,2-penten-4-ynyl, hexyl, isohexyl, 5-methylhexyl, heptyl, and octylgroups. These aliphatic hydrocarbon groups may have one or moresubstituents, for example, aliphatic hydrocarbon groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, isopentyl, neopentyl and tert-pentyl groups; aromatichydrocarbon groups such as phenyl, o-tolyl, m-tolyl, p-tolyl, xylyl,mesityl, o-cumenyl, m-cumenyl, p-cumenyl, and biphenyl groups; etherssuch as methoxy, trifluoromethoxy, ethoxy, propoxy, isopropoxy, buthoxy,tert-buthoxy, pentyloxy, phenoxy, and benzyloxy groups; esters such asmethoxycarbonyl, trifluoromethoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, acetoxy, trifluoroacetoxy, and benzoyloxy groups; andhalogens such as fluorine, chlorine, bromine, and iodine. Depending onthe whole structures of the cyanine dyes, R₁ and R₂ are differentlyaliphatic hydrocarbons represented by C_(m)H_(2m+1) and C_(n)H_(2n+1),where n and m are natural numbers and counted nine or less in total.Most of the cyanine dyes have relatively-high solubility in non-halogensolvents such as diacetone alcohol (abbreviated as “DAA” hereinafter)and relatively-high decomposition points. The cyanine dyes have acharacteristic of relatively-high heat resistance.

[0019] Z₁ and Z₂ in Formula 1 independently represent a fusednaphthalene ring to form a benzoindolenin ring. Usually, thebenzoindolenin ring independently has either 1H-benzo [e] indoleskeleton or 3H-benzo [g] indole skeleton. One or more hydrogen atoms inthe fused naphthalene ring may be replaced with substituents, and thesubstituents include, for example, aliphatic hydrocarbon groups such asmethyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,tert-butyl, pentyl, isopentyl, neopentyl and tert-pentyl groups; etherssuch as methoxy, trifluoromethoxy, ethoxy, propoxy, isopropoxy, buthoxy,tert-buthoxy, pentyloxy, phenoxy, and benzyloxy groups; esters such asmethoxycarbonyl, trifluoromethoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, acetoxy, trifluoroacetoxy, and benzoyloxy groups; alkylsulfonyl groups such as meythylsulfonyl, ethylsulfonyl, propylsulfonyl,isopropylsulfonyl, buthylsulfonyl, tert-buthylsulfonyl, andpentylsulfonyl groups; alkyl sulfamoyl groups such as methylsulfamoyldimethylsulfamoyl, ethylsulfamoyl, diethylsulfamoyl, propylsulfamoyl,dipropylsulfamoyl, buthylsulfamoyl, dibuthylsulfamoyl, pentylsulfamoyl,and dipentylsulfamoyl groups; halogens such as fluorine, chlorine,bromine, and iodine; and nitro and cyano groups. The cyanine dyes of thepresent invention include cis/trans isomers of the cyanine dyesrepresented by Formula 1.

[0020] X⁻ in Formula 1 represents a suitable counter ion. Depending onuses, such a counter ion is not limited and appropriately selected onthe basis of its solubility in DAA and/or heat resistance. When used inoptical recording media, the counter ion which does not substantiallychange the quality of reflection layers including metals, and moreparticularly, anions comprising two or more kinds of elements aredesirable. Examples of such anions are inorganic acid ions such asphosphoric acid ion, perchloric acid ion, periodic acid ion, hexafluorophosphoric acid ion, hexafluoro antimonic acid ion, hexafluoro stannicacid ion, fluoroboric acid ion, and tetrafluoroboric acid ion; organicacid ions such as thiocyanic acid ion, benzensulfonic acid ion,naphthalenesulfonic acid ion, p-toluenesulfonic acid ion, alkylsulfonicacid ion, benzencarbonic acid ion, alkylcarbonic acid ion,trihaloalkylcarbonic acid ion, alkylsulfonic acid ion,trihaloalkylsulfonic acid ion, and nicotinic acid ion; and organic metalcomplex anions such azo, bisphenyldithiol, thiocatechol chelate,thiobisphenorate chelate, and bisdiol-α-diketone. Judging from stabilitysuch as explosiveness and ease of handling, anions, which comprisefluorine and metal elements selected from those of the 15 group in theperiodic law table such as phosphorus, antimony and bismuth, aredesirable; hexafluoro phosphoric acid ion and hexafluoro antimonic acidion. The cyanine dyes of the present invention bearing these anions as acounter ion are characteristic in that they have relatively-high heatresistance, easy handlability, and solubility in organic solvents suchas DAA.

[0021] Further explaining the counter ion of X⁻, depending on uses,desirable anions for the cyanine dyes of the present invention areorganic metal complex anions which improve light resistance, and moreparticularly, azo organic metal complex anions. In the presentinvention, azo organic metal complex anions mean a series of complexanions which have a metal atom as a central atom and bind one or moreazo compounds as a ligand to the central atom. All azo organic metalcomplex anions, which do not substantially lower light absorptance ofthe cyanine dyes and improve light resistance thereof in practical use,can be used independently of their chemical structures and productionmethods. Azo compounds which bind to a metal atom may be identical ordifferent each other. The azo organic metal complexes are, for example,those represented by Formula 6. Since the azo organic metal complexesrepresented by Formula 6 do not substantially lower light absorptance ofthe cyanine dyes, they can be advantageously used in the presentinvention.

[0022] In Formula 6, Z₃ through Z₆ represent identical or differentaromatic rings or heterocycles which may contain one or moresubstituents. Preferably, the aromatic rings are monocyclic benzenerings, and the heterocycles which contain one or more hetero atomsselected from nitrogen, oxygen, sulfur, selenium and tellurium, forexample, those with isooxazolone skeleton, indazolone skeleton,indandione skeleton, oxazolone skeleton, thionaphthene skeleton,barbituric acid skeleton, hydantoin skeleton, pyrazolone skeleton orrhodanine skeleton.

[0023] The aromatic rings and heterocycles may have one or more of thefollowing substituents; aliphatic hydrocarbon groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, isopentyl, neopentyl, tert-pentyl, 1-methylpentyl,2-methylpentyl, hexyl, isohexyl, and 5-methylhexyl groups; alicyclichydrocarbon groups such as cyclopropyl, cyclobuthyl, cyclopentyl,cyclohexyl, and cyclohexenyl groups; aromatic hydrocarbon groups such asphenyl, biphenyl, o-tolyl, m-tolyl, p-tolyl, o-cumenyl, m-cumenyl,p-cumenyl, xylyl, mesityl, styryl, cinnamoyl, and naphthyl groups;esters such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl,acetoxy, and benzoyloxy groups; substituted or unsubstituted aliphatic,alicyclic or aromatic amino groups such as primary amino, methylamino,dimethylamino, ethylamino, diethylamino, propylamino, dipropylamino,isopropylamino, diisopropylamino, buthylamino, and dibuthylamino groups;alkylsulfamoyl groups such as methylsulfamoyl, dimethylsulfamoyl,ethylsulfamoyl, diethylsulfamoyl, propylsulfamoyl, dipropylsulfamoyl,isopropylsulfamoyl, diisopropylsulfamoyl, butylsulfamoyl, anddibutylsulfamoyl groups; carbamoyl, carboxy, cyano, nitro, hydroxy,sulfo, sulfoamino, and sulfonamido groups.

[0024] Depending on uses, one or more hydrogens in the abovesubstituents may be replaced with the following groups; aliphatichydrocarbon groups such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl,1-methylpentyl, 2-methylpentyl, hexyl, isohexyl, and 5-methylhexylgroups; aromatic hydrocarbon groups such as phenyl, biphenyl, o-tolyl,m-tolyl, p-tolyl, o-cumenyl, m-cumenyl, p-cumenyl, xylyl, mesityl,styryl, cinnamoyl, and naphthyl groups; ethers such as methoxy, ethoxy,propoxy, isopropoxy, buthoxy, isobuthoxy, sec-buthoxy, tert-buttery,pentyloxy, phenoxy, and benzyloxy groups; halogens such as fluorine,chlorine, bromine, and iodine; and carboxy, hydroxy, cyano, and nitrogroups.

[0025] As described above, azo organic metal complex anions representedby Formula 6 can be obtained by combining a metal atom of M with one ormore azo compounds as a ligand, which are identical or different eachother. The metal atom is usually selected from metal elements of the 3through 12 groups in the periodic law table such as scandium, yttrium,titanium, zirconium, hafnium, vanadium, niobium, tantalum, chrome,molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium,osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper,silver, gold, zinc, cadmium and mercury. In the field of opticalrecording media, cobalt and nickel are usually used because they areeasily obtainable and handlable. A and A′ in Formula 6 representidentical or different hetero atoms selected from elements of the 16group in the periodic law table such as oxygen, sulfur, selenium andtellurium, and they can form a coordinate bond by providing an electronpair to the above metal atom and may form an atomic group combined withZ₃ and Z₆.

[0026] The azo organic metal complex anions are, for example, thoserepresented by Chemical Formulae 1 to 12. In using these anions as acounter ion for the cyanine dyes of the present invention, they can beadvantageously used in the present invention because they remarkablyimprove the light resistance of the cyanine dyes at wavelengths of350-850 nm and do not substantially spoil desirable light absorptanceand solubility in organic solvents of the cyanine dyes. All of azoorganic metal complex anions represented by Chemical Formulae 1 to 12can be obtained in a satisfactory yield in accordance with well-knownmethods which provide aniline or aniline derivatives in diazo couplingreaction and allow to react the obtained azo compound in the presence ofsuitable metal salts and bases. Cyanine dyes with azo organic metalcomplex anions as a counter ion are prepared by heating the cyanine dyesof the present invention with anions other than azo organic metalcomplex anions as a counter ion and salts of the above azo organic metalcomplex anions in a suitable solvent at over ambient temperature for0.1-10 hours under stirring condition.

[0027] Concrete examples of the cyanine dyes of the present inventionare those represented by Chemical Formulae 13 to 72, which haveabsorption maximum spectra at a wavelength of 580-600 nm when in asolution form and substantially absorb a visible light with a wavelengthof shorter than 700 nm in a longer wavelength region of the absorptionmaximum when in a thin layer form. These cyanine dyes are very useful aslight absorbents of optical recording media using a visible light with awavelength of shorter than 700 nm as a writing light, and moreparticularly, high-density optical recording media such as DVD-Rs, etc.,which use a laser beam with a wavelength of 630-680 nm as a writinglight. The cyanine dyes of the present invention, which have an organicmetal complex anion, and more particularly, azo organic metal complexanion as a counter ion, remarkably have an ability to improve the lightresistance when compared with other cyanine dyes. Thus, they are usefulas light absorbents in DVD-R and light resistance improvers in recordingmedia such as CD-R which have recording layers composed of cyanine dyesand use a visible light with a wavelength from 700 to 800 nm as awriting light, and usually a laser beam with a wavelength of around775-795 nm. The cyanine dyes of the present invention with organic metalcomplex anions as counter ions (I) can remarkably improve the lightresistance without substantially changing the light absorbability ofoptical recording media when used in combination with the cyanine dyesof the present invention with anions other than azo organic metalcomplex anions as counter ions (II), and more particularly, perchloricacid ion, fluorine and anions selected from metal elements from the 15group in the periodic law table in high-density optical recording media.The weight ratio of the above cyanine dyes (I) and (II) can be loweredand highered within the range from 0.1:1 to 1:0.1, and more preferablyfrom 0.3:1 to 1:0.3.

[0028] These cyanine dyes of the present invention can be prepared byvarious methods. They can be preferably produced through a step to reacta benzoindolenium compound bearing an active methyl group with abenzoindolenium compound bearing a suitable leaving group with aneconomical view point. With the method, the cyanine dyes of the presentinvention can be produced in a desirable yield by reacting a compoundrepresented by Formula 2 having R₁ in Formula 1 with a compoundrepresented by Formula 3 having R₂ in Formula 1; or reacting a compoundrepresented by Formula 4 having R₁ in Formula 1 with a compoundrepresented by Formula 5 having R₂ in Formula 1.

[0029] For example, adequate amounts (usually about equal mols) of thecompounds represented by Formulae 2 and 3 or those represented byFormulae 4 and 5 are placed in a reaction vessel, and the resultingmixture is dissolved in an adequate solvent, and then reacted at ambienttemperature or over ambient temperature under heating and stirringconditions, for example, heating reflux conditions, in the presence of abasic compound such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, potassium carbonate, sodium carbohydrate, ammonia,triethylamine, piperidine, pyridine, pyrrolidine, morpholine, aniline,N,N-dimethylaniline, N,N-diethylaniline, N-methylpyrrolidone, or1,8-diazabicyclo [5.4.0]-7-undecene; an acid compound such ashydrochloric acid, sulfuric acid, nitric acid, methanesulforic acid,p-toluenesulfonic acid, acetic acid, acetic anhydride, propionicanhydride, trifluoroacetic acid, or trifluorosulfonic acid; or a Lewisacid compound such as aluminium chloride, zinc chloride, tintetrachloride, or titanium tetrachloride.

[0030] The following solvents can be used: Hydrocarbons such as pentane,hexane, cyclohexane, octane, benzene, toluene, and xylene; halogencompounds such as carbon tetrachloride, chloroform, 1,2-dichloroethane,1,2-dibromoethane, trichloroethylene, tetrachloroethylene,chlorobenzene, bromobenzene, and α-dichlorobenzene; alcohols and phenolssuch as methanol, ethanol, 1-propanol, 2-propanol-1-butanol, 2-butanol,isobutyl alcohol, isopentyl alcohol, cyclohexanol, ethylene glycol,propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, phenol, benzylalcohol, cresol, diethylene glycol, triethylene glycol, and glycerin;ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran,tetrahydropyran, 1,4-dioxane, anisole, 1,2-dimethoxyethane, diethyleneglycol, dimethyl ether, dicyclohexyl-18-crown-6, methylcarbinol, andethylcarbitol; ketones such as furfural, acetone, ethyl methyl ketone,and cyclohexanone; acids and acidic derivatives such as acetic acid,acetic anhydride, trichloroacetic acid, trifluoroacetic acid, propionicanhydride, ethyl acetate, butyl carbonate, ethylene carbonate, propylenecarbonate, formamide, N-methylformamide, N,N-dimethylformamide,N-methylacetoamide, N,N-dimethylacetoamide hexamethylphosphorictriamide, and phosphoric trimethyl; nitriles such as acetonitrile,propionitrile, succinonitrile, and benzonitrile; nitro compounds such asnitromethane and nitrobenzene; sulfur-containing compounds such asdimethylsulfoxide; and water. These solvents can be appropriately usedin combination, if necessary.

[0031] In general, the reactivity decreases as the volume of solventincreases, while, the uniform heating and stirring becomes difficult anda side reaction causes easily as the volume of solvent decreases. Thus,the volume of solvent is desirably up to 100 times, usually 5 to 50times of the material compounds by weight. The reaction completes within10 hours, usually 0.5-10 hours, depending on the kinds of materialcompounds and reaction conditions. The process of reaction can bemonitored in conventional methods, for example, thin-layerchromatography, gas chromatography, and high-performance liquidchromatography. Thereafter, the cyanine dyes of the present inventionwith desirable counter ions can be obtained from the above reactionmixture directly, and if necessary after treated with conventionalcounter ion-exchange reaction. Thus, all the cyanine dyes represented byChemical Formulae 13 to 72 can be easily obtained by the above methodsin a desirable yield. All the benzoindolenium compounds represented byFormulae 2 to 5 can be prepared, for example, by a method as disclosedin Japanese Patent Kokai No. 316,655/98 applied for by the presentapplicant. In Formulae 2 to 5, X₁ ⁻ and X₂ ⁻ are identically ordifferently suitable counter ions to X⁻ in Formula 1, and L is asuitable leaving group which is usually selected from monovalent groupsof aniline or aniline derivatives such as anilino, p-toluidino,p-methoxyanilino, p-ethoxycarbonylanilino, and N-acetylanilino groups.

[0032] The cyanine dyes thus obtained can be used in the form of areaction mixture without any further treatment, and usually can be usedafter purified by the following conventional methods generally used forpurifying their related compounds; dissolution, extraction, separation,decantation, filtration, concentration, thin-layer chromatography,column chromatography, gas chromatography, high-performance liquidchromatography, distillation, crystallization, and sublimation. Ifnecessary, two or more of them can be used in combination. For use as alight absorbent in high-density optical recording media such as DVD-Rs,etc., the cyanine dyes of the present invention should preferably bedistilled, crystallized, and/or sublimated prior to use.

[0033] Explaining the uses of the cyanine dyes of the present invention,they have characteristics in that:

[0034] (i) A relatively-high solubility in non-halogenated solvents;solubility of at least 50 mg/ml in DAA at 20° C., and

[0035] (ii) A strongly-high heat resistance; a decomposition point ofover 272° C.

[0036] The cyanine dyes of the present invention substantially absorb avisible light with a wavelength of shorter than 700 nm, and moreparticularly, a visible light with a wavelength of 630-680 nm when in athin layer form. Thus, the cyanine dyes of the present invention can bewidely used in a variety of fields such as optical recording media,photochemical polymerizations, solar batteries and dyeings, whichrequire the dye compounds with the above characteristics. In these uses,they are very useful as a light absorbent in high-density opticalrecording media such as DVD-Rs which use a visible light with awavelength of shorter than 700 nm as a writing light, and moreparticularly, one with a wavelength of 630-680 nm.

[0037] Explaining the use in optical recording media, the cyanine dyesof the present invention can be used for preparing optical recordingmedia in accordance with the processes for conventional ones becausethey do not require any special treatment and processing. For example,the cyanine dyes of the present invention as a light absorbent can bemixed with one or more other organic dye compounds with the propertiesof substantially absorbing a visible light so as to modulate thereflection and/or absorption by a recording layer, along with one ormore light-resistant improvers, binders, dispersing agents, flameretardants, lubricants, antistatic agents, surfactants, thermalinterference inhibitor, and plasticizers, if necessary. The resultingmixtures are then dissolved in organic solvents, and the solutions arehomogeneously coated over either surface of substrates in such a mannerof using spraying, soaking, roller coating, or rotatory coating method;and dried to form thin layers as recording layers made of lightabsorbents, and if necessary, followed by forming reflection layers tobe closely attached on the recording layers by means of vacuumdeposition, chemical vapor deposition, sputtering, or implanting methodusing metals and alloys such as gold, silver, copper, platinum,aluminum, cobalt, tin, nickel, iron, and chromium to impart a reflectionefficiency of 45% or more, and preferably 55% or more; formingreflection layers to be closely attached on the recording layers byusing commonly used materials for organic reflection layers; or coatingover the recording layers ultraviolet ray hardening resins orthermosetting resins, which contain flame retardants, stabilizers,and/or antistatic agents, to protect the recording layers fromscratches, dusts, spoils, etc., and then hardening the coatings byeither irradiating light or heating to form protection layers to beclosely attached on the reflection layers. In substrates with therecording-, reflection- and protection-layers formed as described above,each protection layer is attached together with adhesives or adhesivesheets, etc, or a protective plate with the same material and form as asubstrate is attached to a protection layer, if necessary.

[0038] As another organic dye compounds usable together with the presentcyanine dyes, any organic dye compounds can be used as long as theysubstantially absorb a visible light and can modulate a light reflectionrate and a light absorption rate of a recording layer of an opticalrecording medium. As the above organic dye compounds, the followingcompounds can be used in an appropriate combination, if necessary:Acridine dye, azaannulene dye, azo dye, anthraquinone dye, indigo dye,indanthrene dye, oxazine dye, xanthene dye, dioxazine dye, thiazine dye,thioindigo dye, tetrapyrapolphyradine dye, triphenylmethane dye,triphenylthiazine dye, naphthoquinone dye, phthalocyanine dye,benzoquinone dye, benzopyran dye, benzofuranone dye, porphyrin dye,rhodamine dye, and cyanine dye in which the same or different rings arebound to both ends of a polymethine chain such as monomethine,dimethine, trimethine, tetramethine, pentamethine, hexamethine, orheptamethine. The chains and rings may have one or more substituents.Examples of the rings are imidazolin ring, imidazole ring,banzoimidazole ring, α-naphthimidazole ring, β-naphthimidazole ring,indole ring, isoindole ring, indolenine ring, isoindolenine ring,benzoindolenine ring, pyridinoindolenine ring, oxazoline ring, oxazolering, isooxazole ring, benzooxazole ring, pyridinooxazole ring,α-naphthoxazole ring, β-naphthoxazole ring, selenazoline ring,selenazole ring, benzoselenazole ring, α-naphthselenazole ring,β-naphthselenazole ring, thiazoline ring, thiazole ring, isothiazolering, benzothiazole ring, α-naphththiazole ring, β-naphththiazole ring,tellurazoline ring, tellurazole ring, benzotellurazole ring,α-naphthtellurazole ring, β-naphthtellurazole ring, acridine ring,anthracene ring, isoquinoline ring, isopyrrole ring, imidanoxaline ring,indandione ring, indazole ring, indaline ring, oxadiazole ring,carbazolering, xanthine ring, quinazoline ring, quinoxaline ring,quinoline ring, chroman ring, cyclohexanedion ring, cyclopentandionring, cinnoline ring, thiodiazole ring, thiooxazolidone ring, thiophenering, thionaphthene ring, thiobarbituric acid ring, thiohydantoin ring,tetrazole ring, triazine ring, naphthalene ring, naphthyridine ring,piperazine ring, pyrazine ring, pyrazole ring, pyrazoline ring,pyrazolidine ring, pyrazolone ring, pyran ring, pyridine ring,pyridazine ring, pyrrolidine ring, pyrylium ring, pyrrolidine ring,pyrroline ring, pyrrole ring, phenazine ring, phenanthridine ring,phenanthrene ring, phenanthroline ring, phthalazine ring, pteridinering, furazane ring, furan ring, purine ring, benzene ring, benzoxazinering, benzopyran ring, morpholine ring, and rhodanine ring.

[0039] The light-resistant improvers used in the present invention are,for example, nitroso compounds such as nitrosodiphenylamine,nitrosoaniline, nitrosophenol, and nitrosonaphthol and metal complexessuch as tetracyanoquinodimethane compounds, diimmonium compounds, and“NKX-1199”(bis[2′-chloro-3-methoxy-4-(2-methoxyethoxy)dithiobenzyl]nickel)produced by Hayashibara Biochemical Laboratories, Inc., Okayama, Japan,and formazane metal complexes, which all can be appropriately used incombination, if necessary. Preferable light-resistant improvers arethose which contain formazane metal compounds, and most preferable onesare formazane compounds, which have a pyridine-ring at C-5 and apyridine- or furan-ring at C-3 of a formazane skeleton as disclosed inJapanese Patent Application No. 163,036/99 (PCT Kokai No. WO00/75111),titled “Formazane metal complexes” applied for by the present applicant;and complexes to metals such as nickel, zinc, cobalt, iron, copper, andpalladium, which have one or more tautomers of the aforesaid compoundsas a ligand. In the case of using such a light-resistant improver incombination, the cyanine dyes of the present invention can beeffectively prevented from undesirable changing in deterioration,fading, color changing, and quality changing, which are inducible byenvironmental lights such reading- and natural-lights, without loweringthe solubility of the cyanine dyes in organic solvents and substantiallydeteriorating preferable optical characteristics. More particularly,formazane metal complexes effectively improve the following features inhigh-density optical recording media in combination with a mixture ofthe cyanine dyes of the present invention having the aforesaid organicmetal complex anions as a counter ion and the cyanine dyes of thepresent invention having anions other than azo organic metal complexanions as a counter ion:

[0040] (i) light resistance of the cyanine dyes of the presentinvention,

[0041] (ii) sensitivity of optical recording media,

[0042] (iii) modulation characteristic,

[0043] (iv) resolution, and

[0044] (v) electrical characteristics such as a jitter characteristic.

[0045] As the composition ratio, 0.01-1 moles, and preferably 0.03-0.3moles of a light-resistant improver(s)-can be incorporated into one moleof the present cyanine dye(s) while increasing or decreasing the ratio.Depending on uses, the cyanine dyes of the present invention withorganic metal complex anions as a counter ion, and more particularly,azo organic metal complex anions, have a relatively-high lightresistance in themselves, and thus the aforesaid light-resistantimprovers may not be required or required with only a small amount.

[0046] The cyanine dyes of the present invention have satisfactory-highsolubility in organic solvents without substantially causing negativeproblem for actual use, and do not substantially restrict organicsolvents used for coating the cyanine dyes on substrates. Thus, in thepreparation of optical recording media according to the presentinvention, suitable organic solvents can be selected from the followingones which are appropriately used in combination: DAA and TFP frequentlyused to prepare optical recording media and the following organicsolvents other than DAA and TFP: For example, hydrocarbons such ashexane, cyclohexane, methylcyclolhexane, dimethylcyclohexane,ethylcyclohexane, isopropylcyclohexane, tert-butylcyclohexane, octane,cyclooctane, benzene, toluene, and xylene; halogen compounds such ascarbon tetrachloride, chloroform, 1,2-dichloroethane, 1,2-dibromoethane,trichloroethylene, tetrachloroethylene, chlorobenzene, bromobenzene, andα-dichlorobenzene; alcohols and phenols such as methanol, ethanol,2,2,2-trifluoroethanol, 2-methoxyethanol (methyl cellosolve),2-ethoxyethanol (ethyl cellosolve), 2-isopropoxy-1-ethanol, 1-propanol,2-propanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butanol,1-methxy-2-butanol, 3-methoxy-1-butanol, 4-methoxy-1-butanol, isobutylalcohol, isopentyl alcohol, cyclohexanol, ethylene glycol, propyleneglycol, glycerine, phenol, benzyl alcohol, and cresol; ethers such asdiethyl ether, diisopropyl ether, tetrahydrofuran, tetrahydropyran,1,4-dioxane, anisole, 1,2-dimethoxyethane, diethylene glycol dimethylether, dicyclohexyl-18-crown-6, methylcarbinol, and ethylcarbitol;ketones such as furfural, acetone, ethyl methyl ketone, andcyclohexanone; esters such as ethyl acetate, butyl acetate, ethylenecarbonate, propylene carbonate, and trimethyl phosphate; amides such asformamide, N-methyl formamide, N,N-dimethylformamide, andhexamethylphosphoric triamide; nitriles such as acetonitrile,propionitrile, and succinonitrile; nitro compounds such as nitromethaneand nitrobenzene; amines such as ethylene diamine, pyridine, piperidine,morpholine, and N-methylpyrrolidone; and sulfur-containing compoundssuch as dimethylsulfoxide and sulfolane. These organic solvents can beused in an appropriate combination.

[0047] Particularly, the cyanine dyes of the present invention haverelatively-high solubility in easily-volatile organic solvents such asTFP and DAA, and thus they are substantially free of crystallizationwhen dissolved in the above organic solvents, spun coated on substrates,and then dried without substantially causing dye crystals andinconsistency of the thickness and the surface of the layers formed onoptical recording media. When the cyanine dyes of the present inventiondissolve in the alcohols such as DAA before coated on the substrates,the solvents do not damage the substrates and pollute the environment.

[0048] Conventional substrates can be used in the present invention andusually processed with suitable materials, for example, into discs, 12cm in diameter and 0.1-1.2 mm in thickness, to suite to final use by themethods such as compression molding, injection molding,compression-injection molding, photopolymerization method (2P method),thermosetting integral method, and lightsetting integral method. Thesediscs can be used in single or plural after appropriately attached themtogether with adhesive sheets or adhesive agents, etc. In principal, anymaterials for substrates can be used in the present invention as long asthey are substantially transparent and have a transmissivity of at least80%, and preferably at least 90% or more at wavelengths ranging from 400nm to 800 nm. Examples of such materials are glasses, ceramics, andothers such as plastics including polyacrylate, polymethyl methacrylate,polycarbonate, polystyrene (styrene copolymer), polymethylpenten,polyester, polyolefin, polyimide, polyetherimide, polysulfone,polyethersulfone, polyarylate, polycarbonate/polystyrene alloy,polyestercarbonate, polyphthalatecarbonate, polycarbonateacrylate,non-crystalline polyolefin, methacrylate copolymer,diallylcarbonatediethylene-glycol, epoxy resin, and phenolic resin,where polycarbonate is most frequently used. In plastic substrates,concaves for expression of synchronizing signals and addresses of tracksand sectors are usually transferred to the internal circle of the tracksduring their formation. The form of concaves is not specificallyrestricted and is preferably formed to give 0.3-0.8 μm in average wideand 70-200 nm in depth.

[0049] The light absorbents of the present invention can be preparedinto 0.5-5 w/w % solutions of the organic solvents as mentioned abovewhile considering the viscosity of the solutions, and then uniformlycoated onto a substrate to form a dried recording layer with 10-1,000nm, and preferably 50-300 nm in thickness. Prior to the coating, apreliminary layer can be formed over the substrate to improve theprotection and the adhesion-ability to the substrate, if necessary.Materials of the preliminary layer are, for example, high-molecularsubstances such as ionomer resins, polyamide resins, vinyl resins,natural resins, silicon, and liquid rubbers. In the case of usingbinders, the following polymers can be used alone or in combination in aweight ratio of 0.01-10 times of the cyanine dye(s): Cellulose esterssuch as nitrocellulose, cellulose phosphate, cellulose sulfate,cellulose acetate, cellulose propionate, cellulose lactate, cellulosepalmitate, and cellulose acetate/propionate; cellulose ethers such asmethyl cellulose, ethyl cellulose, propyl cellulose, and butylcellulose; vinyl resins such as polystyrene, poly(vinyl chloride),poly(vinyl acetate), poly(vinyl acetal), poly(vinyl butyral), poly(vinylformal), poly(vinyl alcohol), and poly(vinyl pyrrolidone); copolymerresins such as styrene-butadiene copolymers, styrene-acrylonitrilecopolymers, styrene-butadiene-acrylonitrile copolymers, vinylchloride-vinyl acetate copolymers, and maleic anhydride copolymers;acrylic resins such as poly(methyl methacrylate), poly(methyl acrylate),polyacrylate, polymethacrylate, polyacrylamide, and polyacrylonitrile;polyesters such as poly(ethylene terephthalate); and polyolefins such aspolyethylene, chlorinated polyethylene, and polypropylene.

[0050] Explaining the method for using the optical recording mediaaccording to the present invention, the high density optical recordingmedia of the present invention such as DVD-Rs can write informations ata relatively-high density by using a visible light with a wavelengthshorter than 700 nm, and more particularly, a laser beam with awavelength around 630-680 nm irradiated by semiconductor lasers such asthose of AlGaInP, GaAsP, GaAlAs, InGaP, InGaAsP or InGaAlP; or YAG lasercombined with second harmonic generation inducing element (SHG element).To read recorded informations, laser beams are used with wavelengthsidentical to or slightly longer or shorter than those used for writinginformations. As for the laser power for writing and readinginformations, in the optical recording media of the present invention,it is preferably be set to a relatively-high level, which exceeds thethreshold of the energy required for forming pits, to write information,while it is suitably be set to a relatively-low level, i.e., a level ofbelow the threshold when used for reading the recorded informations,although the power levels can be varied depending on the types andratios of the light-resistant improvers used in combination with thecyanine dyes: Generally, the levels can be controlled to powers at least5 mW, and usually 10-50 mW for writing; and to powers of 0.1-5 mW forreading. The recorded informations are read by detecting the changes ofboth the reflection light level and the transmission light level in thepits and the pit-less part on the surface of optical recording media bythe light pick-up method.

[0051] Accordingly, in the present optical recording media, minute pitswith a pit width of below 0.834 μm/pit and a track pitch of below 1.6 μmthat is commonly used in a standard CD-R, can be formed at arelatively-high density by a light pick-up using a visible light with awavelength of shorter than 700 nm, and particularly a laser beam with awavelength around 630-680 nm. For example, using a substrate, 12 cm indiameter, it can realize an extremely-high density optical recordingmedium with an optical recording capacity far exceeding 0.682 GB (gigabytes) per one side i.e., a recording capacity of about two hours ofinformation of voices and images, the level of which could hardly beattained by conventional cyanine dyes.

[0052] Since the optical recording media of the present invention canrecord information of characters, images, voices, and other digital dataat a relatively-high density, they are extremely useful as recordingmedia for professional and family use to record, backup, and keepdocuments, data, and computer softwares. Particular examples of thetypes of industries and the forms of information to which the opticalrecording media can be applied are as follows: Drawings of constructionsand engineering works, maps, ledgers of loads and rivers, aperturecards, architectural sketches, documents of disaster protection, wiringdiagrams, arrangement plans, informations of news papers and magazines,local information, and construction specifications, which all relate toconstructions and engineering works; blueprints, ingredient tables,prescriptions, product specifications, product price tables, part'slists, information for maintenance, case study files of accidents andtroubles, manuals for claims, production schemes, technical documents,sketches, details, company's house-made product files, technicalreports, and analysis reports, which are all used in productions;information of companies, records of stock prices, statisticaldocuments, contracts, customer's lists, documents ofapplication/notification/licenses/authorization, and business reports,which are all used in money; information of real property andtransportations, sketches of constructions, maps, and local information,which are all used for customer's information for sales; diagrams ofwritings and pipe arrangements for electric and gas supplies, documentsof disaster protection, tables of operation manuals, documents ofinvestigations, and technical reports; medical cartes, files of clinicalhistories and case studies, and diagrams for medical care/institutionrelationships; texts, collections of questions, educational documents,and statistical information, which are all used in private andpreparatory schools; scientific papers, records in academic societies,monthly reports of researches, data of researches, documentary recordsand indexes thereof, which are all used in universities, colleges, andresearch institutes; inspection data, literatures, patent publications,weather maps, analytical records of data, and customer's files, whichare all used for information; case studies on laws; membership lists,history notes, records of works/products, competition data, and data ofmeetings/congresses, which organizations/associations; sightseeinginformation and traffic information, which are all used for sightseeing;indexes of homemade publications, information of news papers andmagazines, who's who files, sport records, telop files, and scripts,which are all used in mass communications and publishers; and maps,ledgers of roads and livers, fingerprint files, resident cards,documents of application/notification/license/authorization, statisticaldocuments, and public documents, which are all used in governmentoffices. Particularly, the write-once type optical recording media ofthe present invention can be advantageously useful for storing recordsof cartes and official documents, and used as electric libraries for artgalleries, libraries, museums, broadcasting stations, etc.

[0053] As a rather specific use, the optical recording media of thepresent invention can be used to edit compact discs, digital videodiscs, laser discs, MD (a mini disc as an information recording systemusing photomagnetic disc), CDV (a laser disc using compact disc), DTA(an information recording system using magnetic tape), CD-ROM (aread-only memory using compact disc), DVD-ROM (a read-only memory usingdigital video disc), DVD-RAM (a writable and readable memory usingdigital video disc), digital photos, movies, video softwares, audiosoftwares, computer graphics, publishing products, broadcastingprograms, commercial messages, game softwares, etc.; and used asexternal program recording means for large size of computers and carnavigation systems.

[0054] Hereinbefore described are the application examples of thecyanine dyes of the present invention to the field of organic opticalrecording media which use laser beams with wavelengths of shorter than700 nm as a writing light. However, in the field of optical recordingmedia, the cyanine dyes of the present invention can be alsoadvantageously used as materials for changing or regulating the opticalabsorption rate or optical reflection rate in the optical recordingmedia such as commonly used CD-Rs and other high-density opticalrecording media by using in combination, for example, together with oneor more other organic dye compounds which are sensitive to laser beamswith wavelengths of 775-795 nm. When optical recording media are coatedby using laser beams with longer wavelengths such as laser beams withwavelengths of 775-795 nm as a writing light, the cyanine dyes of thepresent invention can be used not to directly form pits on substratesbut to indirectly form pits in such a manner that the excitation energyof laser beams with wavelengths around 630-680 nm is allowed to transferto the aforesaid organic dye compounds via the cyanine dyes by using thecyanine dyes along with one or more other organic dye compounds whichare sensitive to a light with a longer wavelength, e.g., a laser beamwith a longer wavelength of 775-795 nm, resulting in a decomposition ofthe organic dye compounds. The optical recording media as referred to inthe present invention mean optical recording media in general which usethe characteristics of the cyanine dyes of the present invention thatsubstantially absorb a visible light with a wavelength shorter than 700nm in addition to organic optical recording media, thermal colorationmethod using the chemical reaction of coloring agents and developersusing the heat generated when organic dye compounds absorb light, andthe technique called “moth-eye type technique” which uses the phenomenonof that the above heat smooths the pattern of periodical unevennessprovided on the surface of the substrates.

[0055] As described above, the cyanine dyes of the present invention areuseful as a light-resistant improver in recording media such as CD-Rswhich have recording layers composed of cyanine dyes and use a visiblelight with a wavelength from 700 nm to 800 nm as a writing light, andusually a laser beam with a wavelength around 775-795 nm. In the opticalrecording media, the cyanine dyes used in combination with the cyaninedyes of the present invention are, for example, pentamethine cyaninedyes in which the same or different 1H-benzo [e] indole skeleton or3H-benzo [g] indole skeleton are bound to both ends of a pentamethinechain, as disclosed in Japanese Patent Kokai Nos. 203,692/91,203,693/91, 239,149/93, and 199,045/94 applied for by the same applicantas the present invention. As an additive volume of the cyanine dyes ofthe present invention for these cyanine dyes, the light resistance isnot desirably improved when the additive volume is arelatively-low-level, while the electrical characteristic of opticalrecording media is deteriorated when the additive volume is arelatively-high level. Usually, 0.5-50%(w/w), and preferably 3-30%(w/w),of the cyanine dye(s) of the present invention can be incorporated intoother cyanine dye(s) while increasing or decreasing the volume. As alight-resistant improver, one or more other light-resistant improverscan be used with the cyanine dyes of the present invention, ifnecessarily. For example, formazane metal complexes are more desirablyused because they exert good amorphousness and relatively-high heatresistance to the cyanine dyes of the present invention and othercyanine dyes when formed in a thin layer.

[0056] When the cyanine dyes of the present invention are used as alight-resistant improver which uses a visible light with a wavelength oflonger than 700 nm as a writing light such as CD-Rs, they are notnecessarily incorporated into a recording layer. For example, thecyanine dyes of the present invention are incorporated into apreliminary layer, or they are dissolved in suitable solvents with oneor more of the aforesaid binders, and the solutions are coated on thewhole or the part of surface irradiated by a writing light to form aprotection membrane composed of the cyanine dyes of the presentinvention, if necessarily. The preliminary layer and the protectionmembrane can protect a recording layer from environmental lights such asnatural- and artificial-lights and remarkably improve durability ofoptical recording media, and more particularly electricalcharacteristics such as a jitter characteristic and a rate of blockerror. When the solution is covered on the outside of substrate,informations such as characters, figures, pictures, numerals, andsymbols can be printed or written on the outside of substrate by usingthe solution as a printing material or paint.

[0057] Since the cyanine dyes of the present invention substantiallyabsorb a visible light with a wavelength shorter than 700 nm, the lightabsorbents containing the cyanine dyes according to the presentinvention can be used in the aforesaid optical recording media and alsoused as materials for polymerizing polymerizable compounds by exposing avisible light, photosensitizing solar batteries, and dying clothes, aswell as materials for laser active substances in dye lasers. Ifnecessary, in combination with one or more other light absorbentscapable of absorbing light in ultraviolet, visible and/or infraredregions, the light absorbents can be used in clothes in general andothers including building/bedding/decorating products such as a drape,lace, casement, print, casement cloth, roll screen, shutter, shopcurtain, blanket, thick bedquilt including comforter, peripheralmaterial for the thick bedquilt, cover for the thick bedquilt, cottonfor the thick bedquilt, bed sheet, cushion, pillow, pillow cover,cushion, mat, carpet, sleeping bag, tent, interior finish for car, andwindow glasses including car window glass; sanitary and health goodssuch as a paper diaper, diaper cover, eyeglasses, monocle, andlorgnette; internal base sheets, linings, and materials for shoes;wrappers; materials for umbrellas; parasols; stuffed toys; lightingdevices; filters, panels and screens for information displaying devicessuch as televisions and personal computers which use cathode-ray tubes,liquid crystal displays, electrolytic luminous displays, and plasmadisplays; sunglasses; sunroofs; sun visors; pet bottles; refrigerators;vinyl houses; lawns; optical fibers; prepaid cards; and peeping windowsin electric ovens, and other type ovens. When used as wrappingmaterials, injection materials, and vessels for the above products, thelight absorbents of the present invention prevent living bodies andproducts from troubles and discomforts caused by environmental lightssuch as natural- and artificial-lights or even lower the troubles anddiscomforts, and furthermore they can advantageously regulate the color,tint, and appearance and control the light reflected by or passedthrough the products to a desirable color balance.

[0058] The following examples describe the preferred embodiments of thepresent invention:

EXAMPLE 1

[0059] Cyanine Dye

[0060] Thirty milliliters of acetonitrile were placed in a reactionvessel, mixed with 15 g of1-buthyl-3,3-dimethyl-2-[(phenylamino)ethenyl]benzoindolenium=tosylate,and 10.4 g of 1-ethyl-2,3,3-trimethylbenzoindolenium=tosylate, and thenadmixed with 3.3 ml of acetic anhydride at ambient temperature understirring conditions. The resulting mixture was admixed with 9.7 ml oftriethylamine drop by drop and reacted for one hour. Thereafter, thereaction mixture was appropriately admixed with water, allowed to standfor a while, slanted to remove an aqueous phase, appropriately admixedwith methanol, and dissolved under heating conditions. The resultingsolution was filtrated, and the filtrate was admixed with 20 ml of asolution including 11.3 g of ammonium phosphate hexafluoride drop bydrop under stirring conditions. The solution was reacted by heating at70° C. in a thermo-bath for 30 min and cooled to ambient temperature.After the reaction, the formed crystal was collected by filtration anddried to obtain 10.5 g of a golden-green crystal of the cyanine dyerepresented by Chemical Formula 19.

[0061] A part of the crystal was measured in a conventional manner for amelting point, resulting in a melting point of 245-252° C.

EXAMPLE 2

[0062] Cyanine Dye

[0063] Twelve grams of a golden-green crystal of the cyanine dyerepresented by Chemical Formula 20 was obtained similarly as in Example1 except for replacing 11.3 g of ammonium phosphate hexafluoride with9.14 g of potassium antimonate hexafluoride.

[0064] A part of the crystal was measured in a conventional manner for amelting point, resulting in a melting point of 228-232° C.

EXAMPLE 3

[0065] Cyanine Dye

[0066] One hundred twenty milliliters of acetonitrile were placed in areaction vessel, mixed with 12.2 g of the azo compound represented byChemical Formula 77, and 4.0 g of cobaltous diacetate tetrahydrate, andfurther admixed with 11.7 ml of triethylamine drop by drop at 65° C.under stirring conditions and reacted for one hour under the sameconditions. Thereafter, the reaction mixture was filtrated, and thefiltrate was distilled to remove acetonitrile and to give 2/3 of thevolume. The resulting solution was mixed with 100 ml of ethanol todisperse and left at ambient temperature for a time. The formed crystalwas collected by filtration, washed with ethanol and water, and dried toobtain a greenish brown crystal of a triethylammonium salt of the azoorganic metal complex anion represented by Chemical Formula 4. A part ofthe crystal was measured in a conventional manner, and thetriethylammonium salt have an absorption maximum with a wavelength of479 nm when dissolved in methanol, and have a melting point of 327.8° C.

[0067] Two hundred milliliters of acetonitrile were placed in a reactionvessel, mixed with 5.0 g of the cyanine dye represented by ChemicalFormula 41, and 337 ml of an acetonitrile solution including 6.75 g of atriethylammonium salt of azo organic metal complex anion represented byChemical Formula 4, and reacted by heating at 80′ under stirringcondition. After the reaction, the resulting solution was distilled toremove acetonitrile, and the residue was mixed with 400 ml of ethanol,heated at 60° C. for 30 min, and cooled to ambient temperature. Theformed crystal was collected by filtration, washed with ethanol andwater, and dried to obtain 9.4 g of a bright green crystal of thecyanine dye represented by Chemical Formula 43 with an azo organic metalcomplex anion as a counter ion.

EXAMPLE 4

[0068] Cyanine Dye

[0069] Forty milliliters of acetonitrile were placed in a reactionvessel, mixed with 7.08 g of the azo compound represented by ChemicalFormula 78, and 2.57 g of cobaltous diacetate tetrahydrate, and furtheradmixed with 7.5 ml of triethylamine drop by drop at 65° C. understirring conditions and reacted for one hour under the same conditions.Thereafter, the reaction mixture was filtrated, and the filtrate wasdistilled to remove acetonitrile and to give ⅔ of the volume. Theresulting solution was mixed with 80 ml of ethanol to disperse and leftat ambient temperature for a while. The formed crystal was collected byfiltration, washed with ethanol and water, and dried to obtain agreenish brown crystal of a triethylammonium salt of the azo organicmetal complex anion represented by Chemical Formula 6. A part of thecrystal was measured in a conventional manner, revealing that thetriethylammonium salt had an absorption-maximum with a wavelength of 465nm when dissolved in methanol and had a melting point of 270.2° C.

[0070] Two hundred milliliters of acetonitrile were placed in a reactionvessel, mixed with 6.2 g of the cyanine dye represented by ChemicalFormula 15, and 1,000 ml of an acetonitrile solution containing 10 g ofthe triethylammonium salt of azo organic metal complex anion representedby Chemical Formula 6 as mentioned above, and reacted by heating at 80°C. under stirring conditions. After the reaction, the resulting solutionwas distilled to remove acetonitrile and to give 2/3 of the volume andleft for a while to cool down. The formed crystal was collected byfiltration, washed with ethanol, and dried to obtain 4.8 g of a brightgreen crystal of the cyanine dye represented by Chemical Formula 22 withan azo organic metal complex anion as a counter ion.

EXAMPLE 5

[0071] Cyanine Dye

[0072] Forty milliliters of acetonitrile were placed in a reactionvessel, mixed with 10 g of the azo compound represented by ChemicalFormula 79, and 3.98 g of cobaltous diacetate tetrahydrate, and furtheradmixed with 8.47 ml of triethylamine drop by drop at 65° C. understirring conditions and reacted for one hour under the same conditions.Thereafter, the reaction mixture was treated similarly as in Example 3to obtain a greenish brown crystal of the triethylammonium salt of azoorganic metal complex anion represented by Chemical Formula 12. A partof the crystal was measured in a conventional manner, revealing that thetriethylammonium salt had an absorption maximum with a wavelength of 537nm when dissolved in methanol.

[0073] One hundred fifty milliliters of acetonitrile were placed in areaction vessel, mixed with 2.3 g of the cyanine dye represented byChemical Formula 33, and 500 ml of an acetonitrile solution containing2.2 g of the triethylammonium salt of azo organic metal complex anionrepresented by Chemical Formula 12, and reacted by heating at 80° C.under stirring conditions. The reaction mixture was treated similarly asin Example 3 to obtain 9.4 g of a bright greenish brown crystal of thecyanine dye represented by Chemical Formula 35.

[0074] Although the production conditions and yields are varied in somedegrees depending on the structures of the cyanine dyes of the presentinvention, all the cyanine dyes of the present invention, including thecompounds represented by Chemical Formulae 13 to 72, can be produced bythe methods in Examples 1 to 5 or in accordance therewith.

EXAMPLE 6

[0075] Light Absorption Characteristic of Cyanine Dye

[0076] The cyanine dyes as listed in Table 1 of the present inventionwere measured for visible absorption spectra when dissolved in methanoland formed into layers over glasses. In parallel, conventional relatedcompounds represented by Chemical Formulae 73 to 76 were measured forvisible absorption spectra. The maximum absorption spectra in eachconditions are tabulated in Table 1. FIGS. 1 and 2 showvisible-absorption spectra of the cyanine dye of the present inventionrepresented by chemical Formula 20 and the conventional related compoundrepresented by Chemical Formula 74 respectively, when dissolved inmethanol.

TABLE 1 Maximum absorption Cyanine dye wavelength (nm) SolubilityDecomposition Compound R₁ R₂ X⁻ Solution Thin layer (mg/ml) point (° C.)Remarks Chemical Formula16 CH₃ CH₃ Chemical Formula 4 584 605 1.1 314.5Present invention Chemical Formula42 CH₃ CH₃ Chemical Formula 1 590 6120.26 317.7 Present invention Chemical Formula43 CH₃ CH₃ Chemical Formula4 591 617 2.7 304.7 Present invention Chemical Formula13 CH₃ C₄H₉ PF₆ ⁻586 613 143 264.7 Present invention Chemical Formula14 CH₃ C₄H₉ SbF₆ ⁻586 613 73 279.8 Present invention Chemical Formula19 C₂H₅ C₄H₉ PF₆ ⁻587 610 23 281.6 Present invention Chemical Formula20 C₂H₅ C₄H₉ SbF₆ ⁻587 612 140 281.8 Present invention Chemical Formula21 C₂H₅ C₃H₇Chemical Formula 4 587 611 2.8 307.9 Present invention ChemicalFormula29 C₃H₇ C₃H₇ SbF₆ ⁻ 588 613 36 293.3 Present invention ChemicalFormula30 C₃H₇ C₄H₉ PF₆ ⁻ 588 613 15 289.4 Present invention ChemicalFormula31 C₃H₇ C₄H₉ SbF₆ ⁻ 588 613 141 285.0 Present invention ChemicalFormula50 C₄H₉ CH₃ CIO₄ ⁻ 593 626 64 261.3 Present invention ChemicalFormula56 C₄H₉ CH₃ Chemical Formula 1 592 625 187 261.4 Presentinvention Chemical Formula53 C₄H₉ C₂H₅ CIO₄ ⁻ 594 627 >200 244.5 Presentinvention Chemical Formula33 C₄H₉ C₄H₉ SbF₆ ⁻ 589 613 61 284.2 Presentinvention Chemical Formula34 C₄H₉ C₄H₉ Chemical Formula 4 587 613 1.1310.6 Present invention Chemical Formula35 C₄H₉ C₄H₉ Chemical Formula12586 613 6.4 280.1 Present invention Chemical Formula38 C₅H₁₁ C₄H₉ CIO₄ ⁻587 613 >190 262.7 Present invention Chemical Formula39 C₅H₁₁ C₄H₉ SbF₆⁻ 588 613 88 281.8 Present invention Chemical Formula40 C₅H₁₁ C₅H₁₁ SbF₆⁻ 588 613 94 257.3 Present invention Chemical Formula73 CH₃ C₄H₉ CIO₄ ⁻585 612 42 242.2 Control Chemical Formula74 C₂H₅ C₄H₉ CIO₄ ⁻ 587 612 22271.5 Control Chemical Formula75 C₃H₇ C₄H₉ CIO₄ ⁻ 588 613 19 269.0Control Chemical Formula76 C₄H₉ C₄H₉ CIO₄ ⁻ 588 613 17 266.1 Control

[0077] As shown in Table 1, all of the cyanine dyes of the presentinvention have absorption maxima at wavelengths around 580-600 nm whendissolved in methanol similarly as in the conventional related compoundsrepresented by Chemical Formulae 73 to 76, and at wavelengths around600-630 nm when formed in a thin layer. As shown in the visibleabsorption spectra of FIGS. 1 and 2, the absorption end of a longerwavelength region of the cyanine dye of the present inventionrepresented by Chemical Formula 20 extended to a wavelength around 700nm when formed in a thin layer similarly as in the conventional relatedcompounds represented by Chemical Formula 74. These results showed thatthe cyanine dyes of the present invention are useful for high-densityoptical recording media such as DVD-Rs, because they substantiallyabsorb a visible light with a wavelength of shorter than 0.700 nm, andmore particularly, a laser beam with a wavelength around 630-680 nm.

EXAMPLE 7

[0078] Solubility of Cyanine Dye

[0079] For the cyanine dyes in Table 1, they were measured in aconventional manner for solubility in DDA at 20%. In parallel,conventional related compounds represented by Chemical Formulae 73 to 76were also measured for solubility in DAA in a similar way. The resultsare also shown in Table 1.

[0080] As found in the results in Table 1, most of the cyanine dyes ofthe present invention had higher solubilities than those of theconventional related compounds. The solubilities of conventional relatedcompounds were under 50 mg/ml in DAA, while the solubilities of all thecyanine dyes of the present invention measured were almost equal to orhigher than those of the conventional related compounds

EXAMPLE 8

[0081] Decomposition Point of Cyanine Dye

[0082] An adequate amount of any one of the cyanine dyes in Table 1 as atest specimen was placed in a vessel and subjected to conventionaldifferential thermal analysis (hereinafter abbreviated as “DTA”) andthermogravimetric analysis (hereinafter abbreviated as “TGA”) using“MODEL TG/DTA 220”, a digital thermo analyzer commercialized by SeikoInstruments Inc., Tokyo, Japan, to determine their decomposition points,i.e., temperatures at which the cyanine dyes as test specimens begin tolose their weight on TGA. In parallel, conventional related compoundsrepresented by Chemical Formulae 73 and 76 were analyzed similarly asabove. The results are also shown in Table 1. FIG. 3 shows the resultsof DTA and TGA of the cyanine dye represented by Chemical Formula 19 ofthe present invention, respectively. In DTA and TGA, the environmentaltemperature was set to an increasing temperature mode at a rate of 10°C./min.

[0083] As shown in Table 1 and FIG. 3, all the conventional relatedcompounds represented by Chemical Formulae 73 to 76 had decompositionpoints under 272° C., while most of the cyanine dyes of the presentinvention measured had remarkably higher decomposition points than thoseof the conventional related compounds, indicating that their heatresistance was relatively-high. Varying depending on glass transitiontemperature of substrate, when used as a light absorbent in opticalrecording media, dyes with a relatively-low heat resistance can begenerally used to write information by using a lower-power laser beam asthe merit, however, as the drawback, when exposed to a laser beam for arelatively-long period of time on reading, the dyes tend to accumulateheat and deform parts around pits and other pitless parts on recordingsurfaces, resulting in large jitters and reading errors. The fact thatthe cyanine dyes of the present invention have relatively-highdecomposition points shows that high-density optical recording mediahaving a relatively-small jitter, insubstantial reading error, andsatisfactory stability of exposure to environmental light such asreading light and natural light can be obtained by using the cyaninedyes of the present invention as a light absorbent.

EXAMPLE 9

[0084] Optical Recording Medium

[0085] The cyanine dye represented by Chemical Formula 15, 19, 20, 31,or 41 was added to TFP to give a respective concentration of 2.0% (w/w),and the mixture was mixed with, as a light resistant improver, aformazane metal complex in which were bound two molecules of a formazanecompound represented by Chemical Formula 80 in an amount of 0.2% (w/w),and heated for a time, followed by ultrasonically dissolving thecontents. The resulting solution was in a conventional manner filtratedby a membrane, homogeneously coated in a rotatory manner over one sideof a polycarbonate disc substrate, 12 cm in diameter and 0.6 mm inthickness, to which had been transferred concaves, 0.74 μm intrackpitch, 0.03 μm in width and 76 nm in depth, for expressingsynchronizing signals and addresses of tracks and sectors, to give athickness of 100 nm by an injection molding. Thereafter, the substratewas spattered with silver to form a reflection layer, 100 nm inthickness, to be closely attached on the surface of the recording layer,and the reflection layer was homogeneously coated in a rotatory mannerwith “DAICURE CLEAR SD1700”, as a known ultraviolet ray hardening resincommercialized by Dainippon Ink and Chemicals, Inc., Tokyo, Japan, andirradiated to form a protection layer to be closely attached on thesurface of the reflection layer, followed by closely attaching andsticking a polycarbonate disc protection plate on the surface of theprotection layer to obtain five types of optical recording media.

[0086] All of the optical recording media of this Example with goodsensitivity, modulation characteristic, resolution, and electricalcharacteristics such as a jitter characteristic have a recordingcapacity of over 4 GB and can write large amounts of information ofdocuments, images, voices, and digitals at a relatively-high density bya light pick-up using a visible light with a wavelength of shorter than700 nm, and more particularly, a laser beam with an oscillationwavelength around 630-680 nm. Microscopic observation of the recordedsurface of the optical recording media of this example, which had beenwritten information by a semiconductor laser element with an oscillationwavelength of 658 nm, revealed that minute pits with a size of less thanone μm/pit were formed at a track pitch of below one μm.

EXAMPLE 10

[0087] Optical Recording Medium

[0088] Five types of optical recording media were obtained similarly asin Example 9 except for replacing a formazane metal complex with aconventional diimmonium compound, “IRG022” by Nippon Kayaku Co., Ltd.,Tokyo, Japan.

[0089] All of the optical recording media of this Example with goodsensitivity, modulation characteristic, resolution, and electricalcharacteristics such as a jitter characteristic have a recordingcapacity of over 4 GB and can write large amounts of information ofdocuments, images, voices, and digitals at a relatively-high density bya light pick-up using a visible light with a wavelength of shorter than700 nm, and more particularly, a laser beam with an oscillationwavelength around 630-680 nm. Microscopic observation of the recordedsurface of the optical recording media of this example, which had beenwritten information by a semiconductor laser element with an oscillationwavelength of 658 nm, revealed that minute pits with a size of less thanone μm/pit were formed at a track pitch of below one μm.

EXAMPLE 11

[0090] Optical Recording Medium

[0091] The cyanine dye represented by Chemical Formula 13, 29, or 50 asa light-resistant improver was added to DAA to give a respectiveconcentration of 2.0% (w/w), and the mixture was heated for a time,followed by ultrasonically dissolving the contents. The resultingresulting solution was in a conventional manner filtrated by a membrane,homogeneously coated in a rotatory manner over one side of apolycarbonate disc substrate, 12 cm in diameter and 0.6 mm in thickness,to which had been transferred concaves, 0.74 μm in trackpitch, 0.03 μmin width and 76 nm in depth, for expressing synchronizing signals andaddresses of tracks and sectors, to give a thickness of 100 mm by aninjection molding. Thereafter, the substrate was spattered with silverto form a reflection layer, 100 nm in thickness, to be closely attachedon the surface of the recording layer, and the reflection layer washomogeneously coated in a rotatory manner with “DAICURE CLEAR SD1700”,as a known ultraviolet ray hardening resin commercialized by DainipponInk and Chemicals, Inc., Tokyo, Japan, and irradiated to form aprotection layer to be closely attached on the surface of the reflectionlayer, followed by closely attaching and sticking a polycarbonate discprotection plate, 12 cm in diameter and 0.6 mm in thickness, on thesurface of the protection layer to obtain three types of opticalrecording media.

[0092] All of the optical recording media of this Example with goodsensitivity, modulation characteristic, resolution, and electricalcharacteristics such as a jitter characteristic have a recordingcapacity of over 4 GB and can write large amounts of information ofdocuments, images, voices, and digitals at a relatively-high density bya light pick-up using a visible light with a wavelength of shorter than700 nm, and more particularly a laser beam with an oscillationwavelength around 630-680 nm. Microscopic observation of the recordedsurface of the optical recording medium of this example, which had beenwritten information by a semiconductor laser element with an oscillationwavelength of 658 nm, revealed that minute pits with a size of less thanone μm/pit were formed at a track pitch of below one μm.

EXAMPLE 12

[0093] Optical Recording Media

[0094] Two types of optical recording media were obtained similarly asin Example 9 except for a light absorbent with an equivalent mixture ofthe cyanine dyes represented by Chemical Formulae 15 and 16 by weight,or the cyanine dyes represented by Chemical Formulae 41 and 43.

[0095] All of the optical recording media of this Example with goodsensitivity, modulation characteristic, resolution, and electricalcharacteristics such as a jitter characteristic have a recordingcapacity of over 4 GB and can write large amounts of information ofdocuments, images, voices, and digitals at a relatively-high density bya light pick-up using a visible light with a wavelength of shorter than700 nm, and more particularly a laser beam with an oscillationwavelength around 630-680 nm. Microscopic observation of the recordedsurface of the optical recording media of this example, which had beenwritten information by a semiconductor laser element with an oscillationwavelength of 658 nm, revealed that minute pits with a size of less thanone μm/pit were formed at a track pitch of below one μm.

[0096] As described above, the present invention was made based on thecreation of novel cyanine dyes and the findings of their industriallyusable characteristics. The cyanine dyes substantially absorb a visiblelight with a wavelength of shorter than 700 nm, have relatively-highsolubility in organic solvents such as DAA and a relatively-high heatresistance. Accordingly, the cyanine dyes of the present invention canbe advantageously used as a light absorbent in optical recording mediain the form of a DVD-R in which stable minute pits should be formed on arestricted recording surface at a relatively-high density by using, as areading light, a visible light with a wavelength of shorter than 700 nm,and more particularly, a laser beam with a wavelength around 630-680 nmin writing information.

[0097] Comparing with CD-Rs now used in this field, the organic opticalrecording media of the present invention, which write information byusing a visible light with a wavelength shorter than 700 nm, and moreparticularly, a laser beam with a wavelength around 630-680 nm, can formmore minute pits at a narrower track pitch, and this results inadvantageous characteristics of that they can record very large amountsof information of characters, images and/or voices at a relatively-highdensity. Thus, the cost per a bit required for recording information canbe beneficially lowered by a large margin.

[0098] Since the cyanine dyes of the present invention remarkablyimprove the light resistance of other cyanine dyes without substantiallyabsorbing visible light with wavelengths of longer than 700 nm, they canbe advantageously used as a light-resistant improver, for example, inCD-Rs, and more particularly, high-speed writable CD-Rs now commerciallyavailable, which have recording layers composed of other cyanine dyesthat substantially absorb visible light with wavelengths of longer than700 nm and need laser beams with wavelengths around 775-795 nm as awriting light.

[0099] The useful cyanine dyes can be easily obtained in a desirableamount by the method of the present invention through a step of reactinga benzoindolenium compound having an active methyl group with abenzoindolenium compound having suitable leaving groups.

[0100] The present invention having such outstanding effects andfunctions is a significant invention that will greatly contribute tothis art.

[0101] While what are at present considered to be the preferredembodiments of the invention have been described, it will be understoodthat various modifications may be made therein, and the appended claimsare intended to cover all such modifications as fall within the truespirits and scope of the invention.

We claim:
 1. An optical recording medium, which comprises a trimethinecyanine dye represented by Formula 1 and has a solubility of at least 50mg/ml in diacetone alcohol at 20° C.:

wherein in Formula 1, R₁ and R₂ independently represent an optionallysubstituted aliphatic hydrocarbon group; Z₁ and Z₂ independentlyrepresent an optionally substituted naphthalene ring to form abenzoindolenic ring; and X⁻ represents an organic metal complex as acounter ion selected from the group consisting of RF₆ ⁻, ClO₄ ⁻, and Sb₆⁻.
 2. The optical recording medium of claim 1, which is capable ofrecording information thereon by writing thereon with a laser beamhaving a wavelength of around 630 to 680 nm.
 3. The optical recordingmedium of claim 1, which has a decomposition point of over 272° C. 4.The optical recording medium of claim 1, which has a reflectionefficiency of at least 45%.
 5. The optical recording medium of claim 1,which further contains 0.03 to 0.3 mole of a light-resistant improver toone mole of said trimethine cyanine dye.